Fuel cells have been used as a power source in many applications. A typical fuel cell stack is comprised of a plurality of individual fuel cells stacked one upon the other and held in compression with respect to each other. Typically, each fuel cell comprises an anode layer, a cathode layer, and an electrolyte interposed between the anode layer and the cathode layer. The fuel cell stack requires a significant amount of compressive force to squeeze the fuel cells of the stack together. The need for the compressive force comes about from the internal gas pressure of the reactants within the fuel cells plus the need to maintain good electrical contact between the internal components of the cells.
To apply the compressive force, the fuel cell stack is positioned between a pair of rigid endplates that are held in a fixed space relation to maintain a compressive force on the fuel cell stack. Electrically conductive terminal plates are disposed between the endplates and the fuel cell stack and are used to conduct electrical current between the fuel cell stack and the system in which the fuel cell assembly is employed. The fuel cell stack requires gaseous reactants (anode reactant and cathode reactant) to be supplied to and from the fuel cell stack to produce electricity. A coolant flow is also provided to and from the fuel cell stack to keep the stack at a desired operating temperature. These gaseous reactants and coolant can be humid flows and are supplied to the fuel cell stack by manifolds. The manifolds pass through one of the endplates and are sealed against the terminal plate. The gaseous reactants and coolant can then be supplied to the fuel cell stack via the manifolds. Because the seal area is against the terminal plate, the humid fluids (gaseous reactants and/or coolant) are in contact with the terminal plate. Ambient conditions and the voltage (electrical potential), which is applied to the terminal plates, create electrolysis and causes corrosion of the terminal plate. Corrosion of the terminal plate is undesirable because it could decrease the lifespan of the fuel cell assembly and also contaminate the feed streams being supplied to the fuel cell stack through the manifolds. Corrosion is most prevalent in the terminal plate at the location of contact with the coolant flow.
The terminal plates are made from a good conductor, (e.g., aluminum) to facilitate the current flow between the fuel cell stack and the system in which the fuel cell assembly is employed. To protect the terminal plates against corrosion, various coatings have been used on the terminal plate. The coatings to inhibit corrosion, however, can be expensive and cost prohibitive (e.g., made of gold). Additionally, the coatings can have a limited lifespan such that the life of the fuel cell assembly is reduced even with the use of the coatings. Furthermore, the coatings can be very sensitive to minor damage, such as scratches, and result in poor performance or allowing the corrosion process to occur. Thus, an inexpensive way to inhibit and/or prevent corrosion of a terminal plate is desirable.